Sanitary-ware such as baths and sinks conventionally have an overflow opening or channel in the wall of the bowl or tub. The position of the overflow determines the maximum level to which water can be contained in the bathtub or sink bowl. Typically, the overflow is an opening which provides an outlet for excess water, such that flooding by overfilling the sink or the bath can be averted. The opening is generally connected to a waste system either by means of a channel formed in the body of the sink or bath or by means of a flexible hose interconnecting an overflow terminal and a terminal on the waste system.
Such overflow systems are simple and well understood, but they do have some disadvantages. An overflow channel within the body of the bath or sink adds complexity to the structure and to the manufacturing process. A separate flexible hose arrangement uses a number of components and can be awkward to install and maintain. In addition, the waste opening in the wall of the bath or the sink presents potential hygiene problems and can be difficult to clean. In addition, the connection of the opening to the waste system may not be sized appropriately to remove the water at a sufficient rate to avoid the bath or sink overflowing thereby causing potential flooding.
Progress has been made where concealed or external overflow arrangements are being used such that a hole through the body of a sink or bath is no longer required. Such arrangements connect an overflow system to a trap connected to the waste outlet of the bath or sink.
In a commercial setting, for example in a hotel, overfilling a bath can be problematic, where bathrooms can be flooded if the bath is overfilled at great expense to the hotel owners. Therefore, using an external overflow can regulate the maximum fill level of a bathtub such that expensive repairs due to flooding and water damage can be avoided in a commercial setting; such repairs may run into thousands of pounds. Similarly, the risk of flooding also applies in a domestic setting, for example in a family bathroom. Therefore, better control of the maximum water level in a bathtub is desired.